1. Field of the Invention
The present invention relates to a dust and dirt collecting unit for a vacuum cleaner, and more particularly, to a dust and dirt collecting unit for a vacuum cleaner wherein a filter in the cyclonic dust and dirt collecting unit can be protected from impact by foreign substances and its interior constitution can be more simplified.
2. Description of the Prior Art
A vacuum cleaner is an apparatus for sucking air containing foreign substances by means of vacuum pressure, which is generated by a vacuum motor installed within a main body of the vacuum cleaner, and then filtering out the foreign substances from the air in the main body thereof. Further, a paper filter taking the shape of an envelope has been generally used as a filter for filtering out the foreign substances to be sucked. Such a paper filter can filter out the foreign substances such as dust and dirt contained in the sucked air, because the paper filter is designed to allow the air to penetrate therethrough but the foreign substances to remain therein.
However, the vacuum cleaner with the paper filter used therein has inconvenience in use in that if the foreign substances are accumulated within the paper filter to a predetermined level after a certain period of use, suction power of the vacuum cleaner is reduced and thus the paper filter must be periodically replaced with a new one.
In order to solve the inconvenience, a vacuum cleaner in which the filtering action is performed in a cyclonic fashion has been proposed. FIG. 1 shows a conventional cyclonic vacuum cleaner.
As shown in the figure, the vacuum cleaner comprises a main body 20 in which a suction means for sucking the air in the room is installed, a connection hose 34 which is made of a flexible material and connected to communicate with the interior of the main body 20, a variable length extension tube 32 installed to communicate with an end of the connection tube 34, and a suction nozzle 31 for sucking the air containing foreign substances from a floor by means of suction power generated from the main body 20.
Further, a dust and dirt collecting unit 21 that is detachably mounted is installed in the rear of the main body 20. The dust and dirt collecting unit 21 is formed with a handle 21a for allowing a user to grasp the dust and dirt collecting unit when mounting or demounting the unit to or from the rear of the main body 20 of the vacuum cleaner. The dust and dirt collecting unit 21 is a part for causing the air containing the foreign substances sucked from the suction nozzle 31 to be introduced thereinto and then performing the filtering of the foreign substances. At a side of the main body 20 is formed a discharge portion 29 for discharging the air, from which the foreign substances are filtered out in the dust and dirt collecting unit 21, to the atmosphere.
A pair of wheels 28 for causing the main body 20 to travel on the floor are rotatably installed on the bottom of the main body 20. Further, a power cord 26 through which the vacuum cleaner is supplied with electric power is installed at the other side of the main body 20. The power cord 26 is installed such that it can be wound around a cord reel (not shown) in the main body and be received in the main body. A handle 24, which the user can grip when intending to carry the vacuum cleaner, is also installed at a top surface of the main body 20.
When the vacuum cleaner constructed as such is operated, the suction power is transmitted to the suction nozzle 31 through the connection hose 34 and the extension tube 32 by means of the vacuum pressure generated in the main body. Here, the suction power can be adjusted by a switch 33a that is installed on a grip portion 33 coupled with an upper portion of the extension tube 32.
The air containing the foreign substances on the floor to be cleaned is introduced into the main body 20, through the suction nozzle 31, the extension tube 32 and the connection hose 34, by means of the suction power. Then, the air is introduced into the dust and dirt collecting unit 21. Next, the conventional dust and dirt collecting unit 21 will be discussed with reference to FIG. 2.
The conventional dust and dirt collecting unit 21 includes a dust casing 23 of which a top portion is open and which takes the shape of a container, and a cover 22 capable of opening and closing the top portion of the dust casing 23. The dust casing 23 is provided with an inlet 23a through which the air containing the foreign substances sucked from the suction nozzle 31 is introduced. The inlet 23a is formed in a direction tangential to the dust and dirt collecting unit 21 so that the air introduced into the dust and dirt collecting unit 21 can flow in the form of spiral airflow within the dust and dirt collecting unit.
A pair of semicircular separating plates 23b, 23c are installed at a lower portion of the interior of the dust casing 23. The separating plates 23b, 23c can be supported within the dust casing 23, by causing central shafts 23d, 23e of the separating plates to be pivotally mounted onto an inner circumferential surface of the dust casing 23. Further, the separating plates 23b, 23c are supported in a horizontal state and also installed such that they can pivot on the central shafts 23d, 23e only upwardly from the shown horizontal state. For example, the separating plates 23b, 23c may be horizontally supported by means of supporting projections (not shown) formed on the inner circumferential surface of the dust casing 23.
Thus, the separating plates 23b, 23c can pivot only upwardly from the horizontally supported state by means of the supporting projections that protrude from the inner circumferential surface of the dust casing 23.
A dust and dirt collecting space for collecting the foreign substances therein is defined at the lower portion of the interior of the dust casing 23 by the separating plates 23b, 23c. Further, a communicating passage 23f through which the foreign substances can fall down into the dust and dirt collecting space is formed at one side of the separating plate 23b. 
Furthermore, an outlet 22a is formed in the center of the cover 22. The outlet 22a is a part which is formed such that the air from which the foreign substances have been filtered out in the dust casing 23 can be discharged through the discharge portion 29.
A cylindrical filter 25 is installed below the outlet 22a. The filter 25 is also detachably mounted to a bottom surface of the cover 22 so that the cylindrical interior thereof can be in communication with the outlet 22a. 
Next, the operation of the conventional vacuum cleaner and the dust and dirt collecting unit 21 constructed as such will be discussed. If a motor placed in the main body 20 of the vacuum cleaner is operated and the suction power is then generated, the air containing the foreign substances is introduced through the suction nozzle 31. The air is introduced into the main body 20 via the extension tube 32 and the connection hose 34, and then guided into the inlet 23a of the dust casing 23 described above.
The air stream introduced into the dust casing 23 through the inlet 23a becomes the spiral airflow that flows along the cylindrical inner circumferential surface of the dust casing 23. While the spiral airflow is created as such, the relatively heavy foreign substances fall down into the lower portion of the dust casing 23. Then, these foreign substances fall down onto a floor surface of the dust casing 23 through the communicating passage 23f of the separating plate 23b. 
The air from which the relatively heavy foreign substances are filtered out in the cyclonic fashion passes through the filter 25 installed in the center of the dust casing 23 from the outside to the inside of the filter 25. While the air passes into the filter 25, the fine foreign substances contained in the air are sufficiently filtered out.
The air guided into the cylindrical filter 25 is discharged through the outlet 22a formed on a top surface of the cover 22. The air discharged through the outlet is used to cool the motor in the main body 20 while passing by the motor. Then, the air is completely discharged from the main body 20 through the discharge portion 29.
As the vacuum cleaner is operated according to such a process, the foreign substances are accumulated in the dust casing 23. That is, the foreign substances filtered out in the cyclonic dust-collecting manner are accumulated below the separating plates 23b, 23c in the dust casing 23. Furthermore, if the amount of the accumulated foreign substances is greater than a predetermined level, the foreign substances must be emptied from the dust casing 23.
To this end, the dust and dirt collecting unit 21 will be separated or demounted from the main body 20. Then, the cover 22 is also separated from the separated dust and dirt collecting unit 21. If the cover 22 is separated, the filter 25 mounted to the bottom surface of the cover can also be separated. Thus, the separated filter 25 may be cleaned or washed, if necessary.
In addition, if the user causes the dust casing 23 to be inverted so as to empty the foreign substances from the dust casing 23, the separating plates 23b, 23c will pivot downward on the supporting shafts 23d, 23e, respectively. Thus, the foreign substances, which have been accumulated below the separating plates in the dust casing before the dust casing is inverted, can be completely emptied.
However, the conventional vacuum cleaner and the dust and dirt collecting unit constructed as such have the following problems.
First, the foreign substances are also contained in the air introduced through the inlet 23a as described above. Herein, the foreign substances contained in the air to be introduced through the inlet 23a have a velocity corresponding to the suction power and may collide against a surface of the filter. If the foreign substances, particularly large and heavy foreign substances, which collide against the surface of the filter as such, come into contact with the surface of the filter, the filter itself may be damaged. Thus, there is a problem in that suction performance or filtering efficiency of the vacuum cleaner may be deteriorated.
Further, it can be easily understood that the separating plates 23b, 23c are further installed within the dust casing 23 so as to perform the dust and dirt collection in the cyclonic fashion. That is, the dust and dirt collecting unit is constructed such that the dust collecting space for accumulating the foreign substances therein is defined at the lower portion of the dust casing 23 by means of the separating plates 23b, 23c which are separately manufactured and then mounted in the dust casing 23.
Therefore, since the pair of separating plates 23b, 23c manufactured separately are installed in the dust casing 23, the number of parts will be substantially increased, and consequently, the manufacturing process becomes complicated. That is, it can be easily understood that the problems such as increase of production costs and limitations on the productivity in the manufacturing process occur due to the increase of the number of parts.